The use of plant DNA barcoding coupled with HRM analysis to differentiate edible vegetables from poisonous plants for food safety

Abstract

Poisonous Urobotrya siamensis Hiepko has caused deaths of consumers due to misidentification in several cases in past years. The poisonous plant shares the vernacular name in Thai “Phak Wan” with two vegetables, Melientha suavis Pierre and Sauropus androgynus (L.) Merr. The morphology of young leaves among these species is also similar. Therefore, consumer safety could be a major concern. We applied DNA barcoding coupled with high-resolution melting (Bar-HRM) analysis to differentiate the poisonous species from the edible species. Four regions of DNA barcodes, rbcL, matK, ITS2 and the psbA-trnH intergenic spacer, were analysed. Bar-HRM primer pairs were designed based on variable sites of the DNA sequence of the chloroplast matK gene. Distinct melting temperatures for U. siamensis, M. suavis and S. androgynus were revealed at 77.94 ± 0.06 °C, 77.47 ± 0.06 °C and 76.80 ± 0.00 °C, respectively, with confidence levels >99%. The method sensitively identified the poisonous U. siamensis species at levels as low as 0.01 ng of DNA template. Bar-HRM analysis was capable of identifying seedlings or young plants from local nurseries and proved to be an efficient method for detection of food processed by heat treatment, including 5 min of stir-frying and 15 min of boiling. This study is the first report showing that Bar-HRM analysis for safety concerns effectively differentiated poisonous plants from edible plants. Moreover, Bar-HRM analysis may be further applied to other vegetables for quality control, from crop production to food control processes.